Barbora Štefková

The hematite phase decorated with iron-doped cerium oxide nanoparticles (F@FC) was precipitated from cerium and iron oxalate intermediate products. The photocatalytic composite of graphitic carbon nitride (gCN) and F@FC was prepared by a simple method involving mixing the two components, followed by thermal treatment at 400 °C. According to electron microscopy, F@FC is composed of a submicron iron oxide (hematite) phase decorated with iron-doped cerium oxide nanoparticles deposited on gCN substrate. A hierarchically structured composite was observed instead of a simple mechanical mixture of α-Fe₂O₃, Fe-CeO₂, and gCN. To observe two types of degradation activity, photocatalytic and Photo-Fenton degradation activity, Rhodamine B (RhB) was applied as the model water pollutant. The influence of the amount of photocatalyst, the RhB concentration, the presence of cations and anions, the pH, and the effect of e⁻, h⁺, •OH, and •O₂⁻ scavenging reactants were studied. The Photo-Fenton degradation exhibited high efficiency across the entire tested pH range, whereas photocatalytic degradation showed comparable activity only at acidic pH. The F@FC-gCN composite catalyst exhibited a high degree of recyclability. The degradation pathways of photocatalytic and Photo-Fenton reactions were suggested by HPLC-MS analysis of the reaction products. A notable finding of this study was the observation that the green-yellow, fluorescent intermediate Rhodamine 110 was formed during the photocatalytic degradation of RhB. However, the high reactivity of the generated •OH radicals during Photo-Fenton degradation has been demonstrated to inhibit the formation of intermediate Rhodamine 110.

To investigate the possibilities of preparing planar surface‐enhanced Raman spectroscopy (SERS) substrates, several types of cellulose‐based commercially available thin‐layer‐chromatography (TLC) layers, microcrystalline cellulose, diethylaminoethyl cellulose and polyethyleneimine impregnated cellulose, were studied as supporting substrates. There is a worldwide need for making various processes, including chemical synthesis, greener. Therefore, cellulose was chosen as the base for SERS substrates for its economic and environmentally friendly characteristics. For the SERS substrates preparation, Tollens' process was used, and as reducing substances, maltose and glucose were used. All the prepared samples were able to detect 10 ⁻⁵ M adenine solution (using 780‐nm laser wavelength), which was chosen as the model analyte to evaluate their SERS efficiency. The highest SERS response was achieved with the sample prepared on microcrystalline cellulose using maltose as the reducing agent. This substrate was subsequently used for determination of adenine limit of detection, with the value of LOD = 10 ⁻⁷ M. Calculated analytical enhancements factor reached up to 10 ⁸ . Moreover, TLC layers represent a semi‐flexible substrate, which can be beneficial for many future applications.